… Hydrometers and similar floating instruments, thermometers, pyrometers, barometers, hygrometers and psychrometers, recording or not, …
Explanatory notes
… 90.25 ‑ Hydrometers and similar floating instruments, thermometers, pyrometers, barometers, hygrometers and psychrometers, … (though some may be of metal, e.g., nickel‑silver, silver, etc.), and weighted at one end with mercury or fine lead …